1. Field of the Invention
The present invention relates to a wired circuit board, more particularly, to a wired circuit board such as a flexible wired circuit board.
2. Description of Related Art
A flexible wired circuit board is a wired circuit board having flexibility and typically comprises a insulating base layer made of a flexible resin film, a conductive pattern made of metal foil formed on a surface of the insulating base layer and an insulating cover layer made of a flexible resin film formed on the surface of the insulating base layer to cover the conductive pattern.
Such a flexible wired circuit board has terminal portions each for connecting to an external circuit or mounting an electronic component, which are provided as the portions of the conductive pattern exposed from openings in the insulating cover layer.
Because the external circuit is connected to the terminal portions or the electronic component is mounted thereon, the portions of the flexible wired circuit board on which the terminal portions are provided need to have a certain level of strength. To satisfy the need, it has been known to bond a reinforcing plate to the back surface of the insulating base layer. For example, it has been proposed to back the terminal portions of a flexible wired circuit board with a reinforcing plate made of an aluminum plate via an adhesive agent (see, e.g., Japanese Unexamined Patent Publication No. 07-170033).
However, when a high rigidity is needed, it is necessary to thicken the reinforcing plate. In the manufacturing of a wired circuit board, there is a case where a number of wired circuit boards are manufactured as in a single sheet and the sheet is wound up and stored in the form of a roll. In such a case, when the reinforcing plate is thick, it is difficult to wind up the sheet into the form of a roll. In addition, when the sheet is stored in the form of a roll, a problem occurs such that the reinforcing plate remains gently curled even after the sheet is unwound and cannot recover its original flat shape.
In addition, the backing of the sheet with the reinforcing plate via the adhesive agent leads to an increase in cost since it requires additional use of the adhesive agent for the backing. Moreover, an extra process step is needed for the backing to cause the problem of a productivity reduction.